In recent years almost all the electric apparatuses have been controlled by inverter circuits from the viewpoint of environmental protection, thereby pursuing energy saving and higher efficiency. The automotive industry, in particular, introduces a hybrid vehicle (HEV), which can be driven by an electric motor and an engine, into the market. In the automotive industry, techniques related to environment, energy saving, and higher efficiency have been actively developed.
The electric motor to be used in the HEV works in a high voltage range, such as several-hundred volts, so that a metalized film capacitor has drawn attention to be used in this electric motor since the metalized film capacitor has features of a high withstanding voltage and a low loss.
Metalized film capacitors are categorized into two types; one type employing a metal foil as an electrode; and the other type employing a metal film made by depositing metal on a dielectric film as an electrode. The metalized film capacitor employing the metal film made by depositing metal as the electrode has an advantage of a smaller volume occupied by the electrode over the other capacitor employing the metal foil. The metalized film capacitor can thus have a small size and a light weight. The metalized film capacitor also has a self-recovery function to an electrode film formed by depositing, namely, the electrode film around a defective area is vapored and scattered, thereby recovering the function of capacitor. This function is referred to as a self-healing property, and enhances reliability against dielectric breakdown. The metalized film capacitor is thus widely used. A thinner electrode film tends to vapor and scatter more easily, so that the self-healing property can be enhanced, having a higher withstanding voltage expected.
FIG. 7 is a perspective view of conventional film capacitor 1. Film capacitor 1 includes capacitor element 5 and a pair of external electrodes 6 formed on both ends of capacitor element 5. Capacitor element 5 includes a pair of metalized films 4 which are wound. Each metalized film 4 includes dielectric film 2 and electrode film 3 formed on dielectric film 2. The pair of metalized films 4 are wound such that electrode films 3 formed in the pair of metalized films 4 face each other across dielectric film 2, then the pair of metalized films 4 are wound. Electrode film 3 of at least one of the pair of metalized films 4 includes electrode segments 7, first fuses 8 connecting electrode segments 7 to each other, and second fuses 9 connecting electrode segments 7 to each other. Electrode segments 7 are arranged in plural columns in first direction 5A in which the pair of external electrodes 6 are arranged. Electrode segments 7 are also arranged in second direction 5B perpendicular to first direction 5A. First fuses 8 connect electrode segments 7 adjacent to each other along first direction 5A while second fuses 9 connect electrode segments 7 adjacent to each other along second direction 5B. When electrode segment 7 out of electrode segments 7 is short-circuited and have an over-current flowing thereto, fuses 8 and 9 connected to the short-circuited electrode segment 7 are fused, thereby isolating the shorted electrode segment 7. This operation allows film capacitor 1 have a high withstanding voltage while the capacitance of the capacitor decreases.
Related art to film capacitor 1 is disclosed in, for instance, Patent Literatures 1 and 2.